High Pressure Die Casting

What is high pressure die casting?

High pressure die casting (HPDC) is a high-volume manufacturing process in which molten aluminium alloy is injected into a hardened steel die at high velocity and high pressure — typically 40 to 120 MPa (6,000 to 17,000 psi), reaching up to 140 MPa on structural or vacuum-assisted machines — and held under pressure until solidification is complete. The process produces thin-walled, complex, net-shape components at cycle times measured in tens of seconds. It is the dominant casting process for high-volume aluminium components in automotive, electronics, lighting, telecoms and consumer goods.

Aluminium HPDC is performed on cold-chamber machines, where the molten metal is ladled into a shot sleeve and injected by a hydraulic plunger. Zinc and smaller magnesium parts use hot-chamber machines, where the injection mechanism sits in the molten metal bath.

HPDC vs. gravity die casting

We supply both processes. They are not interchangeable, and the right choice depends on volume, geometry and end-use requirements.

	HPDC	Gravity die casting
Process	High-velocity, high-pressure injection into a hardened steel die	Gravity pour into a reusable steel (permanent) mould
Wall thickness	1.0–4.0 mm typical, down to 0.8 mm on small features	3 mm minimum typical; thicker sections supported
Cycle time	15–90 seconds depending on part size	Typically 2–5 minutes per cycle
Tooling cost	High — justified at tens of thousands of parts per year and above	Moderate — viable from a few hundred parts per year
Surface finish	Excellent as-cast (Ra 1.6–3.2 µm), suitable for paint, powder coat, anodise	Good as-cast (Ra 6.3 µm or better)
Internal soundness	Dense outer skin, residual gas/shrinkage porosity in section centres — not suitable for PED pressure-bearing applications or heavy machining of internal features	Pressure-tight internal soundness suitable for PED-certified pressure-bearing components after T6 heat treatment
Typical alloys	A380, 383, A360, ADC12, LM24, 413	LM25 / A356, LM6, LM9, LM4
PED compliance	Not supplied under PED	PED 2014/68/EU certified (TÜV Rheinland NB 0035)

If your component carries pressure or requires PED 2014/68/EU conformity, gravity die casting is the correct process. See our PED-certified aluminium gravity die castings → for that scope of work.

Aluminium alloys we HPDC

The major HPDC alloy families are AlSi8Cu3 and AlSi9Cu3 type alloys, alongside lower-copper variants for improved corrosion resistance. We routinely supply:

• A380 / EN AC-46000 (AlSi9Cu3(Fe)) / ADC10 — by far the most widely used HPDC alloy. Excellent castability, good machinability, good combination of strength and economics. The default choice for general industrial components, housings, brackets and covers. AC-46500 — the same chemistry envelope with up to ~3 % Zn (ADC10Z) — is supplied where the customer permits the Zn allowance.
• 383 / EN AC-46100 (AlSi10Cu2Fe) / ADC12 — improved die-filling capacity for thin-wall and intricate parts; better resistance to hot cracking. The standard alloy in much of Asia and widely used for thin-wall structural housings.
• A360 / EN AC-43400 (AlSi10Mg) / ADC3 — lower copper content; better corrosion resistance and weldability than A380, somewhat harder to cast. Used where the part will see a corrosive environment.
• LM24 (AlSi8Cu3Fe) — UK / BS 1490 equivalent of A380, frequently specified by UK and European customers.
• 413 / EN AC-47100 (AlSi12Cu1(Fe)) — near-eutectic alloy, excellent fluidity and pressure tightness, used for thin-wall and intricate components where strength requirements are modest.

Other HPDC alloys can be sourced to specification. Full chemical and mechanical certification is supplied with every batch, issued against EN 1706, ASTM B85 or equivalent as required.

Sizes, tolerances and finish

Single-piece weight	Few grams up to approximately 5 kg in standard production; larger possible on dedicated machines — discuss at quotation
Linear tolerance (as-cast)	Approximately ±0.1 mm on small features, growing with size; tighter tolerances available on critical features by agreement
Wall thickness	1.0–4.0 mm typical; 0.8 mm minimum on small features
Draft	1–2° on external walls, 2–3° on internal walls and cored holes
Surface finish	Ra 1.6–3.2 µm as-cast, suitable for paint, powder coat or anodise without further preparation
Cored holes	Cast as standard to reduce or eliminate drilling
Threads	External threads can be cast; internal threads tapped after casting
Inserts	Steel inserts, bushings and threaded inserts can be cast in place

The "skin effect" — design implications

HPDC components have a dense, fine-grained outer skin approximately 0.4–0.5 mm thick with mechanical properties significantly higher than the centre of the section. Beneath the skin, residual gas porosity from die filling and solidification shrinkage is normal and acceptable for the vast majority of HPDC applications. This has two practical consequences:

• Minimise machining stock. Heavy machining cuts through the strong, dense skin and exposes the more porous core. We design machining allowances to remove no more than 0.5–1.0 mm where structural performance matters.
• HPDC is not pressure-tight by default. For components that must contain pressurised liquids or gases, gravity die casting (with PED certification where required) is the correct process — not HPDC.

Design guidelines

HPDC favours specific design choices that reduce defects and tooling cost:

• Uniform wall thickness — variations in section cause differential cooling, shrinkage porosity and warpage. Aim for ±10 % of the nominal wall
• Generous fillets and radii — minimum 1.5 mm internal fillets to prevent stress concentration and improve metal flow
• Ribs in preference to thick sections — ribs add stiffness without creating heavy mass that traps porosity
• Draft on all surfaces parallel to die pull direction — non-negotiable for ejection
• Avoid undercuts where possible — they require slides or moving cores, which add tooling cost and cycle time
• Place cored holes in the line of die pull where possible to avoid the need for slides
• Discuss parting line at the design stage — parting line position affects cosmetic surfaces, tolerance and tooling cost

We will review your drawing at the quotation stage and recommend changes that reduce cost and improve castability before tooling is cut.

Typical applications

• Automotive — gearbox and transmission housings, oil sumps, timing covers, brackets, EV battery housings, structural body components (where vacuum-assisted HPDC is used)
• Electronics and telecoms — heat sinks, equipment enclosures, antenna housings, optical and electrical cabinet components
• Power tools and consumer goods — gear cases, motor housings, body shells
• Lighting — luminaire bodies, heat dissipation components for LED fixtures
• Industrial machinery — non-pressure pump and compressor housings, valve bodies, OEM brackets and covers

Quality, testing and certification

Every HPDC production order is produced to a defined quality plan. Standard capabilities include:

• ISO 9001:2015 quality management system
• Chemical analysis by optical emission spectrometer on every melt
• Mechanical testing — tensile strength, proof stress, elongation and hardness
• Dimensional inspection on coordinate-measuring machine (CMM)
• Non-destructive testing — dye penetrant (PT) and X-ray on request
• Leak testing (air or helium) where specified
• Material and inspection certification to EN 10204 3.1 supplied with every shipment

HPDC components are not supplied under PED 2014/68/EU. If your part falls within the Pressure Equipment Directive, please see our PED-certified gravity die castings →.